Mechanism of Growth Hormone (GH) Action on Erythropoiesis1

Daily administration of 1 mg of bovine GH for 5 days to hypophysectomized rats resulted in a significant stimulation of erythropoiesis; this effect was completely abolished by simultaneous administration of anti—erythropoietin (anti—Ep) serum. Moreover, GH did not potentiate the wave of erythropoiesis evoked by exogenous Ep. Therefore, it is postulated that GH exerts its effect through stimulation of Ep production, rather than by influencing Ep action on erythropoiesis. In line with this concept, Ep plasma levels were elevated in hypophysectomized rats receiving 4 daily injections of 1 mg of GH. A comparable increase in plasma Ep was detected in ureter—ligated animals, while no detectable Ep was present in nephrectomized rats receiving GH. Finally, elevated levels of the renal erythropoietic factor (REF or erythrogenin) were noted in kidney extracts from hypophysectomized rats receiving 1 mg of GH for 4 days. It is concluded that the stimulation of erythropoiesis evoked by GH is mediated through an increased production of Ep. (Endocrinology91: 511, 1972)